Electric switchboards



June 18, 1957 A. R. DAVIS 2,796,473

ELECTRIC swITcHBoARns Filed Nov. 16, 1954 2 sheets-sheet 1 35 3,2 fMlmlllany* IN VEN TOR.

June 18, 1957 A. R. DAVIS 2,796,473

ELECTRIC SWITCHBOARDS Filed NOV. 16. 1954 2 Sheets-Sheet 2 2,796,473ELECTRIC swrrcnBoARDs Ariel R. Davis, Provo, Utah Application November16,v 1954,*Serial No. 469,201

Claims. (Cl. 20G-16)' This invention relates to. lighting control andparticu-i larly to electric switchboards for providing a4 selection lofcurrent and voltage sources' having diierent values for lights of atheatre or thelilce.` l V It is often desirable yinpthe ,operation ofbanks of lights to change vfrom one level of intensity to anotherdepending on the illumination requiredV aty thattime.

This is particularly true in the case of theatre lights where theillumination requirements may be changed from scene to scene or within ascene. The lights should be accurately land precisely set at the desiredlevel of" lee which are each connected to a separate conducting bar 30of the electric switchboard through the adjustable taps An object of theinvention is to provide an electric,

switchboard which transfers the lights from one setting to anotherwithout contacting any intermediate sources.

Another object of the invention is to connect different sets of lightsto the same dimmer to load the dimmer to full capacity. Y f

Another object of the invention is -to provide a small compactswitchboard that has a minimum of connecting wires yand occupies a smallspace.

A further object of the invention is to providean electric switchboardthat is inexpensive to manufacture and install. y I

Other and further objects and advantages will be apparent from thefollowing specification taken in connection with the accompanyingdrawings, in which:

Fig. l is ya top view of the switchboard; Fig. 2 is a top view of thebase along lines 22 of Fig. 3 with slots and conducting bars; Y

Fig. 3 is a sectional view along lines 3--3 of Fig. l; Fig. 4 is asectional view along lines 4-4 of Fig. 3; Fig. 5 is a sectional viewalong lines 5-5 of Fig. 3; Fig. 6 is a schematic circuit diagram showingthe connections to loads `and to the current adjusting means;

Fig. 7 is a sequential view of the movement of a contact along the base;

Fig. 8 is a fragmentary exploded View of the contact. Fig. 9 is afragmentary sectional view ofthe terminal bar in the grooveor slot inthe base.

Referring to Fig. 6, there is schematically shown an electricswitchboard 17for connecting the lights 10, 11, 12, such as theatrelights, to dimmers 13, 14, 15, 16. The dimmers are connected betweenpower lines 18 and 20 or 19 and 20 and the lights are between the rails22, 23, 24 of the electric switchboard 17 and the power line 20. Theelectric circuit is completed through the adjustable contacts 25, 26,27, 28 of the dimmers 13, 14, :15, 16

13a, 14a, 15a, 16a. The lights through the Vrails 22, 23, 24 are singlyconnected to the bars 30 by the contacts 31, 32, 33 in sliding contactwith the rails and point Contact with the bars 30. Thus, each load maybe connected to any one of the dimmers but not more than one dimmer atone time. l The lights 10, 11, 12 may be connected to the same bar andthe same dimmer at the same time. This provides exibility of selectionof the intensity of illumination of the lights. The taps determine` thevoltage across the light when one of the sliding contacts engages thebar connected to the tap. The taps are set at different positions to tapdifferent voltages from respective dimmers. As thecontacts engage thebars, the different voltages are at different values and are placedacross the lights. Thus, before the performance of a play, the taps arepre-set and during the play a contact may be moved from one bar toanother and correspond ingly change the intensity of illumination.

The lines 18, 19 are connected directly to a respective bar 30 so thatthe lights 10, 11, 12 may have a full line voltage applied to them.

Considering the electric switchboard in detail the electricallyconducting bars 30 are fitted in evenly spaced and parallel slots 36 tocut in the raised longitudinal central portion 37 of the base 38. Thebase is made of a stif, hard electrically insulating material.

,The slots extend across the width of the central portion. On each 'sideof the central portion 37 are cut portions 39 and 40 for the cableterminals 42, 43 connected to the bars 30. The slots are cut deep intothe central portion to form walls 44, and concave portions 46, 47 aredrilled in the bottom of the slots and are a greater distance apart thanthe walls 44, 45 to hold lthe bars. The bars 30 are inserted endwisebetween the concave walls. The bars are recessed in the slot and thewalls 44, 45 have a substantial depth to form an air space or chamber 48which quenc'hes any spark tending to form on breaking of contact withthe bar 30. The bars have eyelets or fastening portions 49 which larepositioned in the cut portions 39, 40 and bolted to the base 38 by'theterminals 42, 43. The terminals of successive bars are alternatelypositioned on opposite sides of the central portion 37 in the cutportions 39, 40, respectively, permitting a close arrangement of thebars and providing space around the terminals 42 or 43. Between theslots are strips 85 spacing the bars 30. The slots 36, strips 85 andbars 30 are parallel and evenly spaced in the intermediate portion ofthe central portion 37 between mounting portions 51 and 52 on oppositeends of the central portion 37. The mounting portions 51, 52 providespace for securing the upper contact holder 53 to the base 38. T'hecontact holder 53 comprises vertically positioned and evenly spacedguides 54 centered longitudinally on the central portion 37 and ttinginto evenly spaced grooves in the top 55 which is secured lto the base38 by bolts 56 threaded in the openings 57 in the mounting portions 51,52. In cooperation with the grooves in the top 5S the guides 54 :areuniformly spaced by spaces 57 tting in between the guides 54 and held bythe bolt 58 and the nut 59 at one end of the contact holder 53 and,similarly, by spaces 61 and similarly fastened by a bolt.62 and nut (notshown) at the olther end. The contacts 31, 32, 33 slide in the parallelslots 63, 64, 65 extending longitudinally in the supporting member 55 topermit the contacts to move transversely to the slots and bars.preferably made of wire and have two legs on opposite sides of therespective slots 63, 64, 65 and parallel thereto. The rails are heldtightly against the top 55 by the spaces 57 and 61. The two long legs oneach side of kpatentar June 1s, 195':`

The rails 22, 23, 24 are` an associated slot provide two longitudinalcontacting surfaces extending the length of the switchboard. At one endeach rail is bent over the respective spacer and secured by a terminalbolt 66 to which the leads to the respective lights are secured. Theguides 54 extend longitudinally beyond the spacer to form recesses 66 toisolate the terminals. n

The contacts 31, 32, 33 are identical in construction and operate in thesame manner, and identical parts of respective contacts operating in thesame way are numbered for simplicity of description. Each Contactcomprises a blade 70 preferably made of a silver alloy fitting into aslot and |silver-soldered to a blade holder 71 having an innercylindrical bore extending substantially half of the length of theholder from the end opposite to the blade 70. The contacts are shown inFigs. 3, 4, 5 yand 8. The slots 72 are formed on opposite sides of the|holder and extend lthe length of the bore and merge with a transverseslot across the holder. A tubular member 73 with a `square head 74 onone end thereof telescopically lits kinto the bore and a helical spring80 fits inside of the tubular member and seats on the bottom of fthebore in the holder to force said 'members apart (Fig. 4). A flat contactplate 74a made of, silver is soldered to the head '74 and engages thetwo surfaces of the rail. The blade 70 ts into the slots in the base 38to engage the bars 30. A braided wire 76 is fitted in a slot 75 in theholder 71 adjacent the blade 70 and has the free ends tting into a slot77 in the head 74 adjacent the contact surface 74u. The braided wire isformed in two flexible leadsto yield with the movement between thetubular member and the holder. n

ln Figs. 3 and 4, the holder 71 and the tubular member 73 are preferablymade of a highly electrically cony' ductive material hard enough towithstand physical usage, such as brass. The tip 71a and the head 74electrically connect the braided wire to the blade 70 and contact plate74a. The blade holder is mounted on a sheet 86 of thin, `stiffinsulating material having a rectangular shape fitting in the opposingslots 72 and seating in the transverseslo't in the blade holder 71, anda bolt 79 extends through the transverse Yslot and isthreaded in theblade holder 71 fastening the sheet 86 thereto. The insulating sheetextends through the slot 63 in the top and has-'a grip 82 of insulatingmaterial fastened by bolts 83 to the exposed end for moving the Contact.The sheet has an elongated vertical opening '84 Iextending from thebottom of the bore of the blade holder 71' to above the rails throughwhich the tubular member 73 moves as the blade 7() is moved in and outof the slots 36 or as the Contact 33 is pivoted about the end of theblade. Y

As shown in Fig. 4, the helical spring 80'is housed in the bores of theholder 71 and tubular member 73 and seats in the bottom of the bores.The spring is under compression when the contact is in position,creating a pressure to maintain the lcontact surface 76 in contact withthe rails and force the blade 70 firmly against the bar 30 when setvertically in the slot 36. The spacers 57 and 61 and the grooves in thetop have a width to space the guides 54 slightly greater than the widthsof the blade holder 71 and blade 70, and the groove 63 has a widthslightly greater than the thickness of the sheet 81 to hold the blade 70parallel to the slots 36 and provide for easy sliding of the contact,The contact moves between the guides 54 without twisting or turning sothat when 'the blade 70 is stopped at a slot 36 the blade will fit intothe slot and engage the bar. The insulatingstrip S5 Vbetween the bars 36spaces the bars and provides a ysurface along which the blade 70 slideswhen the position of the contact is changed. With the grip 813 spaced adistance A from the surface of the top 55, the contact freely pivotsabout the contacting edge `of thev blade 70 when it is either in theslot or resting on the strip 85. The length of the blade holder 71 andthe tubular member 73 in fully compressed position is less than thedistance o-f the Contact surfaces of .the rail from the strip 85. InvFig. 4

the contact 33 is shown in a vertical position, and the at surfacecontact 74a sets `against the rails with the blade on a strip 85. Asshown in Fig. 3 the contact may be tilted towards either end of theswitchboard depending on the direction of movement. The degree of tiltis limited bythe rounded ends of the grip 83 which engage the uppersurface of the supporting member 55.

/ The contact plate 74a is Iunseated and turned to engage holds theblade against the edge of the wall 45 and does not permit the blade 70to dropl down inside the slot and engage a bar 3f).l Thus, as thecontact is moved along the strips 85 the contact surges across the slots36 and does not engage the'bars 30.V `When the desired bar is reachedthe pressure is released and the contact moves back slightly and theblade drops into the slot. The blade engages'a bar and the currentpasses to lights 10, 11, 12. On. breaking contact with thebar 30 thecontact 22 is pivoted about the rounded end of theblade 70 until therounded` edge of the grip '83 engages the top. The contact is furtherpressed and pivoted, sliding the blade along the other edge 44 or 45depending on direction of movement and drawing it on to thel strip 84.The blade holderv 71 and blade 70 may be drawn vertically telescopingthe tubular member 73 and blade holder 71 by pulling up on, the grip 83.The blade is raised clear of the strips and the contact is moved to thenext position and dropped in the desired slot. The slots are'deep sothat a spark occurring on thesep'aration ofthe blade 70 and bar 30 willbe extinguished. The primary current path is through the bar 30, blade70 to the lower end of holder 71 and thence through the braided wireVloops to the block 74 and contact surface 76 which engages the rails 22.

yIn the drawing, three contacts are shown and described. Flfhe centralportion 37 vmay be made wider and the bars 30 lengthened so that anynumber of contacts may be arranged parallel to one another therebyincreasing the number of light loads that may be connected to thedimmers and likewise the central portion may also be lengthened toincrease the number of bars and therefore the number of dimmersconnected to the switchboard. The parallel arrangement of the bars andthe parallel arrangement of the rails lateral to the bars permit a widecombination of lights and dimmers with a minimum of interconnectingwires.

The contacts are light in construction and held between the base and thesupporting member. The rails are preferably made of wire and are heldagainst the top 55, and

' the bars 30 are also preferably made of wire cut in the appropriatelengths and formed with an eye at one end. Thus, a minimum of metal isrequired. The metallic conducting portion formed by the blade 70, theblade holder 71 and the tubular member 73 is between the rail 22 and thebar 30. The grip 83 and insulating sheet which move the contact are madeof a light and stiff insulating material. The blades 70 are wide toprovide a long contact surface on the bar 30 to provide an etticienttransfer of electricity.

It is thus seen that the lights may be transferred from one dimmer toanother without exposing operating personnel to any members carryingvoltages. The changes may be made rapidly and accurately withoutengaging any intermediate bars. Another advantage from the arrangementof parts is that the switchboard is compact with a maximum number oflighting loads connectable to a maximum number of dimmers with a minimumof interconnectmg parts and wires. A minimum amount of metallic parts41s required and the structural members may be readily made from moldedinsulating material. The conducting bars 30 and the rails 22., 23, 24may be considered to be conductive terminal means for passage of thecurrent to the Contact or contact assembly. The slots 36 may beconsidered to be grooves formed by the sides of the strips 85. Otherloads in the lights 10, 11, 12 may be connected to the switchboard andthe voltages thereto controlled by the adjustment of the contacts 31,32, 33. It is not intended to limit the invention to the control oflights although this is the preferred use of the applicants invention.The dimmers providing the voltages through the bars 30 may beconventional rheostats or auto-transformer type voltage devices.

One modification is that the telescoping relation of the tubular memberand blade holder would be reversed.

The tubular member 73 could be the outer member and the blade holder 71could be the inner member.

Various other modifications and changes may be made in the embodiment asdescribed without departing from the invention as set forth in theappended claims.

I claim:

1. A terminal in an insulating base comprising an elongated groove insaid base and having two generally parallel opposing walls on oppositesides of said groove and extending inwardly from the outer portion ofsaid groove and having concave opposing walls extending further inwardlyfrom the inner edge of said parallel walls, a generally cylindricalshaped electrically conductive means a diameter greater than thedistance between said parallel walls and less than the diametricdistance between said concave walls, said means inserted endwise betweensaid concave walls and held therein recessed from the outer edges of theparallel walls to isolate the said means from transient movement of acontacting blade lateral to the parallel walls and provide a sparkquenching chamber above said conductive means.

2. An electric switchboard comprising a base having grooves and flatlateral strips spacing said grooves and having opposing edges, saidgrooves having two opposing walls on opposite sides of each grooveextending inwardly from said opposing edges, electrical conductive meansat the bottom of said grooves, a contact blade having spring meansurging said blade into a groove on engagement therewith and movable atan angle to said base across said strip and grooves with the bladedropping off the edge of a strip and the side of the blade contacting atan angle the opposing edge of the adjacent strip so that the contactblade is held from engaging said electrical conductive means.

3. An electric switchboard comprising a base having an intermediateportion with lateral grooves spaced by flat lateral strips and havingmounting portions at each end, parallel sheet-like guides normal to saidstrips and extending longitudinally along said base transverse to saidgrooves, spacers of uniform thickness between said guides, a supportingmember above said guides having longitudinal grooves fitting on the endsof said guides to cooperate with said spacers to evenly space saidguides to form a channel, rail means extending longitudinally along saidchannel and mounted on said supporting member between said guides,electrically conductive bars recessed in said grooves to form chambersabove said bars and a contact assembly mounted between and laterallysupported by said guides to move through said channel for selectivelyconnecting said bars to said rail and to pivot on said bar to tilt saidcontact in order to clear said bars on longitudinal movement.

4. An electrical switchboard comprising a base having conductive barsrecessed below the surface of the base to form chambers between thesurface and said bars, a supporting member having longitudinallyextending guide means, a contact assembly supported by said guide meansto move laterally to said conductive bars, a contact assembly having acontact portion positionable in said chambers to individually contactsaid conductive bars, said contact assembly laterally supported by saidguide means to move laterally to said bars and pivotally on said base totilt said assembly between said guides at an angle so that on lateralmovement of the assembly the contact portion projects into the groove adistance less than the depth of the chamber to remain out of contactwith said conductive means.

5. An electric switchboard as set forth in claim 2 wherein said contactportion comprises a rectangular blade-shaped member having a width lessthan the space between the walls of said chamber to permit saidbladeshaped member to be tilted in said chamber to engage one of saidedges and pivot said blade on lateral movement to disengage said bladefrom said conductive means.

References Cited in the file of this patent UNITED STATES PATENTS1,158,083 Stout Oct. 26, 1915 1,764,411 Masek June 17, 1930 1,975,564Tritle et al. Oct. 2, 1934 2,487,199 Titcomb Nov. 8, 1949 2,612,557Turner Sept. 30, 1952

